JP2003057206A - Method for determining quantity in alloy phase in plated layer, and sliding property evaluation method in alloying melted zinc-plated steel plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a determination method for the quantity of an alloy phase in a plated layer in plated covering metal materials, such as alloying melted zinc-plated steel plate for directly and accurately determining the quantity of the alloy phase in a plated layer. SOLUTION: In the method for determining the quantity of the alloy phase in the plated layer, a plated film metal material, having a plurality of types of alloy phases in a plated layer, is set to be the anode, the alloy phase in the plated layer is subjected to constant potential electrolysis in each of a plurality of potentials that are determined based on the dipping potential of a ground metal material and that of each alloy phase, and the quantity of each alloy phase in the plated layer is determined for each layer based on the amount of electricity that has flown in each electrolysis potential.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for quantifying an alloy phase (corresponding to a ζ phase, a δ ₁ phase, a Γ phase in a galvannealed steel sheet) in a plating layer of a plated metal material. The present invention relates to a slidability evaluation method.

[0002]

2. Description of the Related Art As a plated layer of a plated metal material,
There are metal single-phase plating layers and plating layers having multiple types of alloy phases. In particular, it is known that, in a plated product having a plurality of types of alloy phases, various characteristics of the product are greatly influenced by the composition and amount of the alloy phase.

Therefore, control of the alloy phase is essential for improving the plating characteristics. Among the surface-treated steel sheets, the plated layer of the alloyed hot-dip galvanized steel sheet that produces a large amount of
This is a typical example of a plating layer having an alloy phase of Zn and Fe and a plurality of alloy phases. Further, in the above-mentioned alloyed hot-dip galvanized steel sheet, the alloy phase that greatly affects various plating characteristics is the alloy phase of Zn and Fe (ζ phase, δ ₁ phase, Γ phase). In particular, the ζ phase has a great influence on the slidability of a galvannealed steel sheet suitable as an anticorrosive steel sheet for automobile bodies.

As a physical method for observing the alloy phase structure of a plated steel sheet, observation of the steel sheet cross section with an optical microscope or a scanning electron microscope is generally used (Akihiko Nishimura, Junichi Inagaki, Kazuhide Nakaoka: iron). And Steel, 8, 101 (1986)). According to such observation, the degree of development of each alloy phase can be qualitatively obtained, and the data of the average thickness of each phase can be quantitatively obtained, but the problem is that the preparation and observation of the sample are complicated. Is.

Further, in recent years, due to the sophistication of the characteristics expected of plated products, a minute amount of alloy phases that adversely affect the plating characteristics has become a problem. That is, in the case of a galvannealed steel sheet, it is necessary to suppress the formation of the ζ phase and the Γ phase, but it is difficult to identify these minute amounts of alloy phases. On the other hand, using the X-ray diffraction method, studies have been conducted to correlate the diffraction intensity of each alloy phase with various characteristics of plating, and its application to online measurement has been attempted.

That is, in the alloyed hot-dip galvanized steel sheet, the relationship between the X-ray diffraction intensity of each alloy phase and the slidability and powdering resistance during the processing of the plated steel sheet was reported (Masato Yamada, Aki Masuko, Hisao Hayashi). , Naoki Matsuura: Materials and Processes, 3,
591 (1990)) and the application of X-ray diffraction to online measurement (Kawabe Sequential, Tadao Fujinaga, Hajime Kimura, Kazuya Oshiba, Tadahiro Abe, Toshio Takahashi: Kawasaki Steel Engineering Report, 18,129 (198).
6)).

However, these methods are not methods for directly obtaining the absolute amount of each alloy phase, and in order to quantify each alloy phase, a calibration curve is prepared using a standard sample whose content of each alloy phase is known. It is necessary to prepare and calculate the content from the strength ratio with the standard sample. That is, for example, in the determination of a very small amount of ζ phase or Γ phase in a galvannealed steel sheet, it cannot be measured without a standard sample whose content of ζ phase or Γ phase is known.

On the other hand, as a chemical method, a constant current anodic electrolysis method (electrolytic stripping method) is used. In this method, a time-potential curve is used to measure a time of a potential flat portion corresponding to each phase, The thickness of each plating alloy phase is determined from the amount of electricity (SCBritton: J.Inst.Metals, 58,211 (1936)). However, in the case of the above method, the inflection point (electrolytic end point of each phase) of the galvannealed steel sheet with a small amount of ζ phase or Γ phase is unclear, and a very small amount such as ζ phase or Γ phase. Phase quantification is difficult.

Further, in the case of this method, it is difficult to uniformly dissolve each alloy phase in the plating layer. In addition, when the above method is applied to the galvannealed steel sheet, it is reported that there is a problem in converting the melting time of the flat portion to the plating thickness as it is because the Γ phase having a high iron concentration remains as a residue. (Susumu Kurosawa: Surface Technology, 45,234 (1994)).

Further, the shape of the time-current curve fluctuates depending on the surface condition of the sample, and it has been more difficult to quantify the alloy phase existing in a very small amount on the outermost surface of the plating, for example, the ζ phase of the galvannealed steel sheet.

[0011]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art by directly changing the alloy phase in the plating layer directly.
Quantitative method and alloying melting of alloying phase in plating layer of plated metal material that can be accurately quantified (zeta phase, δ ₁ phase, Γ phase are applicable in case of galvannealed steel sheet) It is an object to provide a slidability evaluation method for galvanized steel sheets.

[0012]

According to a first aspect of the present invention, a plating-coated metal material having a plurality of alloy phases in a plating layer is used as an anode, based on the immersion potential of a base metal material and the immersion potential of each alloy phase. An alloy in the plating layer characterized by performing a constant potential electrolysis of the alloy phase in the plating layer at each of a plurality of defined potentials and performing phase-specific quantification of each alloy phase in the plating layer based on the amount of electricity flowing at each electrolysis potential. It is a method of quantifying the phase.

A second invention uses an alloyed hot-dip galvanized steel sheet as an anode, electrolytically operates in a zinc sulfate-sodium chloride aqueous solution within a potential range of -940 to -920 mV vs SCE, and flows. A method for quantifying the ζ phase in a plated layer of a galvannealed steel sheet, which comprises quantifying the ζ phase in the plated layer based on the amount of electricity. A third invention uses an alloyed hot-dip galvanized steel sheet as an anode, and in a zinc sulfate-sodium chloride aqueous solution, potential: -940 to -920 mV vs SCE.
The electrolysis operation is performed within the range of the electric potential, and the ζ phase in the plating layer is quantified based on the amount of electricity that has flowed, and then the galvannealed steel sheet that is the anode has a potential of −900 to −840 mV.
Method of quantifying ζ phase and δ ₁ phase in galvanized galvanized steel sheet characterized by quantifying δ ₁ phase in galvanized layer based on the amount of electricity flowing by electrolyzing in the range of electric potential Is.

In a fourth aspect of the present invention, an alloyed hot-dip galvanized steel sheet is used as an anode, and an electrolytic operation is carried out in a zinc sulfate-sodium chloride aqueous solution within a potential range of -940 to -920 mV vs SCE to flow. Quantify the ζ phase in the plating layer based on the amount of electricity, and then electrolyze the alloyed hot dip galvanized steel sheet that is the anode within the range of potential: -900 to -840 mV, and perform plating based on the amount of electricity that flows. Δ ₁ phase in the layer was quantified, and then the galvannealed steel sheet as the anode was electrolyzed within the range of potential: −830 to −800 mV, and the Γ phase in the plated layer was calculated based on the amount of electricity flowing. Is a method for quantifying the ζ phase, δ ₁ phase and Γ phase in the plating layer of the galvannealed steel sheet.

In the above-mentioned first to fourth inventions, it is preferable that the electrolysis is a constant potential electrolysis. A fifth invention uses a galvannealed steel sheet as an anode, and in a zinc sulfate-sodium chloride aqueous solution, potential: -940 to -920 mV vs S.
Electrolytic operation is carried out within the CE potential range, and the amount of electricity flowing is less than a certain amount to make an alloyed hot dip galvanized steel sheet with good slidability. This is a motility evaluation method.

In the above-mentioned fifth invention, the quantity of electricity is
It is preferably 0.5 C / cm ² or less, and the time point at which the current density reaches 5 μm / cm ² is preferably the end point of the electrolysis operation. In addition, vs SCE described as a unit of potential indicates a potential with respect to a saturated calomel electrode.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below. As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that each alloy phase of the plating-coated metal material having a plurality of types of alloy phases exists separately in the thickness direction of the plating layer. It was found that it is possible to electrolyze only each alloy phase at a potential capable of selectively dissolving each alloy phase by utilizing the structure of (3), and to quantify each alloy phase from the amount of electricity flowing at that time, leading to the present invention.

That is, for example, in the case of alloyed hot-dip galvanized steel sheet, constant potential electrolysis is sequentially performed at a potential capable of selectively melting only the ζ phase, δ ₁ phase, and Γ phase alloy phases, and the alloy phases are separated. It was found that it is possible to quantify each alloy phase extremely accurately by measuring the amount of electricity that has melted and flowed at each potential. In addition, the present inventors
The electrolytic behavior of the ζ-phase of galvannealed steel sheets with various slidability was investigated. As a result, they have found that the galvannealed steel sheet having a total amount of electricity (current density × time) up to the completion of electrolysis is a certain amount or less has good slidability.

That is, in the first aspect of the present invention, a plating-coated metal material having a plurality of alloy phases in the plating layer is used as an anode, and a plurality of electrodes are defined based on the immersion potential of the base metal material and the immersion potential of each alloy phase. This is a method for quantifying the alloy phase in the plating layer, in which the alloy phase in the plating layer is subjected to constant potential electrolysis at each potential and the amount of each alloy phase in the plating layer is quantified by phase based on the amount of electricity flowing at each electrolysis potential.

The above-mentioned immersion potential refers to the potential of the metal with respect to the saturated calomel electrode when the metal is immersed in the electrolytic solution, and the above-mentioned plurality of potentials include the immersion potential of the base metal material and the alloy phase. Potentials between the immersion potential and the immersion potential of each alloy phase can be selected. In the above-mentioned first invention, each of the plurality of types of alloy phases does not mix in the plating layer, and each of the alloy phases exists separately in the thickness direction of the plating layer. Is preferred.

This is because, when a plurality of types of alloy phases have the above-mentioned structure, each alloy phase can be separately subjected to constant potential electrolysis from the surface side of the plating layer toward the base metal material at the melting potential of each alloy phase. This is because it is possible to quantify each alloy phase for each phase. As the plurality of potentials described above, the potential between the immersion potential of the base metal material and the immersion potential of the alloy phase on the surface of the base metal material (: the surface immediately above) and the immersion potential of each alloy phase in direct contact with each other Can be selected.

The present inventors have further obtained the following knowledge based on the first invention. That is, the alloyed hot-dip galvanized steel sheet was used as an anode, and in the zinc sulfate-sodium chloride aqueous solution, the ζ phase, δ ₁ phase, and Γ phase, which are alloy phases in the plating layer, were (A) potential: −940 to −920 mV vs. SCE, (B) potential:-
900 to −840 mV vs SCE and (C) potential: −830 to −800 m
Within the respective potential ranges of V vs SCE and in that order, electrolysis is performed, and the ζ phase, δ ₁ phase and Γ phase are calculated based on the amounts of electricity flowing at the respective potentials (A), (B) and (C). A method for phase-wise quantification of phases was developed. That is, the second
The inventions of 4 to 4.

This is because it is necessary to form the δ ₁ phase and suppress the ζ phase and the Γ phase in the galvannealed steel sheet. In the preferable embodiments of the second to fourth inventions described above, it is preferable that the electrolysis is a potentiostatic electrolysis. This is because it is possible to selectively electrolyze each alloy phase by performing constant potential electrolysis.

In the above-mentioned second to fourth inventions, a galvanized metal material such as a galvannealed steel sheet is used as an anode, and the electrolytic potential is appropriately set according to the type of alloy phase in the plated layer, and a predetermined alloy is electrolyzed. Dissolve the phases selectively. In the above-mentioned operation, the amount of electricity until a positive current stops flowing within the range of the electrolytic potential of the predetermined alloy phase (: within the range of the melting potential) is measured.

That is, for example, in the case of a galvannealed steel sheet, the galvanized steel sheet is used as an anode, and the ζ phase is (A) potential: −940 to − in an aqueous solution of zinc sulfate-sodium chloride.
After electrolyzing within the range of 920 mV vs SCE and no positive current flows, after the δ ₁ phase is electrolyzed within the range of (B) potential: -900 to -840 mV vs SCE and no positive current flows , Γ phase
(C) Potential: Electrolyze until a positive current stops flowing within the range of −830 to −800 mV vs SCE.

If the above potential is out of the range of each potential, the predetermined alloy phase is insufficiently melted or it becomes difficult to selectively melt each alloy phase. Next, the abundances of the ζ phase, the δ ₁ phase, and the Γ phase are calculated based on the amount of electricity flowing at each potential (: within the potential range) and the electrochemical equivalent required for melting each alloy phase. Further, based on the obtained calculated value and the surface area of the plated steel sheet, the adhesion amount of the alloy phase per unit area of the plated steel sheet is obtained, or the obtained calculated value, the surface area of the plated steel sheet and the density of each alloy phase Determine the thickness of the alloy phase.

That is, in the case of galvannealed steel sheet
If the following equations (1) and (2)₁Phase and Γ phase
Of the alloy phase (alloy) i (: i = ζ phase)
Is δ ₁Phase or Γ phase) adhesion amount: X_iAnd thickness: Y_i
Can be asked.   X_i(G / m²) = [C / F] × [M / 2] × [10000 / A] ……… (1)   Y_i(Μm) = [C / F] × [M / 2] × [10000 / (ρ × A)] × 10^-6...... ……… (2) In the above formulas (1) and (2), C: Electricity required for melting alloy phase i (C) F: Faraday constant = 96485 (C / mol) M / 2: average equivalent of alloy i (g / mol) A: Dissolved sample area (cm²) ρ: Density of alloy i (g / m³) Electrolysis may be carried out in an appropriately selected electrolyte solution, and the alloy
For hot dip galvanized steel, zinc sulfate-Natri chloride
It is preferable to use an aqueous solution of um.

This is because the use of the zinc sulfate-sodium chloride aqueous solution increases the difference in immersion potential between the ζ phase, the δ ₁ phase and the Γ phase and facilitates the selective dissolution of each alloy phase. Is. In addition, the chemical dissolution action of the plating layer is small, and the plating layer is unlikely to be affected by the oxide film formed on the surface. To obtain such effects sufficiently, the concentration of zinc sulfate is 1 to 50 mass% and the concentration of sodium chloride is 1 to 30.
It is preferably set to mass%.

According to the present invention, the alloy phase can be directly and accurately quantified on the basis of the amount of electricity flowing by electrolysis and the electrochemical equivalent required for melting the alloy phase. Further according to the invention,
Since the alloy phase can be directly and accurately quantified, each alloy phase of the standard sample is quantified by the method of the present invention, and the obtained quantitative value and X
A calibration curve with the diffraction intensity by the line diffraction method is created, and the alloy phase can be quantified online by using the calibration curve and the X-ray diffractometer.

The fifth invention uses an alloyed hot-dip galvanized steel sheet as an anode and performs electrolytic operation in a zinc sulfate-sodium chloride aqueous solution within a potential range of potential: -940 to -920 mV vs SCE, It is a method of evaluating the slidability of an alloyed hot-dip galvanized steel sheet, characterized in that it is evaluated as an alloyed hot-dip galvanized steel sheet having good slidability according to the amount of electricity flowing.

If the amount of electricity flowing during constant potential electrolysis is less than a certain amount, good characteristics can be obtained in various tests for evaluating slidability. As a test for evaluating slidability, a cylindrical flat-bottom cup drawing test can be exemplified. The potentiostatic electrolysis is carried out in a zinc sulfate-sodium chloride system electrolytic solution with a plated plate (alloyed galvanized steel sheet) as the anode and a potential of -940 mV to -920 mV to the saturated calomel electrode. The reason why the potential is changed from -940 mV to -920 mV is to selectively electrolyze and quantify a portion of the alloyed hot-dip galvanized layer that has a great influence on the slidability. The reason for performing electrolysis in a zinc sulfate-sodium chloride-based electrolytic solution is that the chemical dissolution action of the plating layer is small and it is not easily affected by the oxide film formed on the surface. When changing the electrolytic solution, the potential for selectively electrolyzing a portion of the alloyed hot-dip galvanized layer that has a great influence on the slidability changes, so it is necessary to confirm it by a preliminary experiment.

The sixth invention, which is the first preferred aspect of the fifth invention, is characterized in that in the slidability evaluation method of the fifth invention, the quantity of electricity is 0.5 C / cm ² or less. Is a method for evaluating slidability of a galvannealed steel sheet. If it is judged that the slidability is good because the amount of electricity is 0.5 C / cm ² or less, the same judgment is made as when it is judged that the slidability is good in the slidability evaluation in the cylindrical flat-bottom cup drawing test. Can be obtained. When alloy hot-dip galvanized steel sheets having better slidability are evaluated and selected, 0.3 C / cm ² or less may be determined to be good slidability.

In the second preferred embodiment of the fifth invention and the preferred embodiment of the sixth invention, the current density is 5 μA.
The method is for evaluating the slidability of a galvannealed steel sheet, which is characterized in that the end point of the electrolysis operation is the time point when / cm ² is reached. If electrolysis is continued until the current density reaches 5 μA / cm ² , it can be applied to the evaluation of slidability as the measurement result of the substantial amount of electricity. Rather, measuring the quantity of electricity when the current density exceeds 5 μA / cm ² not only increases the cost, but also measures the quantity of electricity involved in the unintended electrolytic reaction, which may lead to incorrect measurement of the quantity of electricity. The nature will increase.

[0034]

EXAMPLES The present invention will be described more specifically below based on examples. Example 1 In this example, each alloy phase (: ζ phase, δ ₁ phase, Γ phase) of the galvannealed steel sheet was quantified by phase by constant potential electrolysis.

As a sample of the galvannealed steel sheet, a circular sample having a diameter of 15 mm was used, and one side of the sample was sealed with a tape for corrosion test and used for the measurement. In addition, as samples, samples of three types of galvannealed steel sheets under different manufacturing conditions (Sample A, Sample B, Sample C) were used, and the thickness of the ζ phase, the δ ₁ phase, and the Γ phase was measured three times for each sample. It was measured.

FIG. 3 shows the electrolysis apparatus used for the measurement by a vertical sectional view (a) and a schematic view (b). In FIG. 3, 1 is an electrolysis device, 2 is a sample, 3 is a platinum ring (counter electrode), 4 is a saturated calomel electrode, 5 is a platinum wire, 6 is an electrolytic solution, and 7 is a reference electrode (RE: Reference Electrode). .

As the electrolytic solution, a 10% ZnSO ₄ -20% NaCl aqueous solution: 50 ml was used. Further, as shown in FIG. 3, a saturated calomel electrode was used as the reference electrode and platinum was used as the counter electrode.
Dissolution of ζ phase: -930 mV vs SCE, dissolution of δ ₁ phase: -860 mV vs SCE, dissolution of Γ phase: -825 mV vs S
The CE was performed in that order, and the amount of electricity until a positive current stopped flowing at each potential was measured for the same sample.

FIG. 4 shows the time-current curve obtained by the above measurement. In addition, Table 1 shows the thickness of each alloy phase calculated by the above formula (2) based on the amount of electricity required for melting each alloy phase and the electrochemical equivalent required for melting each alloy phase, and the standard of thickness for the same sample. Deviation: Shows σ. The above formula
M / 2, A, and ρ in (2) are as follows.

M / 2; ζ phase: 32.2, δ ₁ phase: 32.2, Γ phase: 31.9 (g / mol) A; 1.77 (cm ² ) ρ; ζ phase: 7.18 × 10 ⁶ , δ ₁ phase: 7.25 × 10 ⁶ , Γ phase: 7.36 ×
10 ⁶ (g / m ³ ) As shown in Table 1, according to the present invention, even if the alloy phase in the plating layer is very small, the standard deviation of the quantitative value in the same sample: σ is extremely small, and the alloy phase is directly It was found that it is possible to quantify with high accuracy.

[0040]

[Table 1]

(Example 2) Using six kinds of alloyed hot-dip galvanized steel sheet samples under different manufacturing conditions, the alloy phase of the alloyed hot-dip galvanized steel sheet: ζ phase by the method of the present invention similar to the above-mentioned Example 1 , Γ phase was quantified, and the thickness of the alloy phase was calculated.
In addition, using six types of alloyed hot-dip galvanized steel sheets in the same lot as the sample described above, the alloy phase:
X-ray diffraction intensity of ζ phase and Γ phase (ζ phase: d = 1.26Å, Γ phase:
d = 2.59Å) was measured.

Next, a calibration curve of the quantitative value (thickness of alloy phase) obtained by the method of the present invention and the X-ray diffraction intensity was prepared. The calibration curve obtained above is shown in FIG. 1 and FIG.
As shown in FIGS. 1 and 2, it was found that there is a good correlation between the quantitative value of the alloy phase obtained by the method of the present invention and the X-ray diffraction intensity.

From the above results, the alloy phase can be accurately quantified online using the calibration curve and the X-ray diffractometer obtained based on the method of the present invention. (Example 3) A galvannealed steel sheet used as a test material was produced by the following method. An ultra-low carbon steel sample material was melted in a converter and then continuously cast into a slab. This slab was wound at 550 ° C with a slab heating temperature of 1150 to 1250 ° C and a final finishing temperature of 920 ° C in the hot rolling process. A 3.2 mm-thick hot-rolled sheet coil was prepared, and after removing the black skin by pickling, it was cold-rolled to obtain a 0.8 mm-thick cold-rolled sheet. This steel sheet was used as a plating original plate in a continuous hot dip galvanizing line at an annealing temperature of 790 to 830 ° C. Penetration plate temperature into the plating bath is 460 to 470 ℃, bath temperature of the plating bath is 460 to 470 ℃, alloying temperature is 490 to 530 ℃
And The coating amount on one surface was 40 to 50 g / m ^2, and the coating amount on both surfaces was the same.

The alloyed hot-dip galvanized steel sheet produced as described above was punched into a circle of 15 mmφ, and then -930 mV vs SCE
At constant potential electrolysis. The electrolyte contains 20 mass% zinc sulfate-10
A mass% sodium chloride aqueous solution was used. Current density is 5μ
Electrolysis was carried out until A / cm ² or less, and the amount of electricity flowing from the start of electrolysis was measured. The time required for electrolysis was about 10 to 20 minutes.

The slidability of the galvannealed steel sheet whose electric quantity was measured was evaluated. After applying 1.5 g / m ² of ordinary rust preventive oil to the alloyed hot-dip galvanized steel sheet, a 33 mmφ cylindrical flat-bottom cup drawing test was performed to determine the limiting drawing ratio. The smaller the limit drawing ratio, the better the slidability. Limiting aperture ratio 2.0% or more ... 1, 1.9 to 2.0
%… 2, 1.8 to 1.9%… 3, 1.7 to 1.8%… 4, 1.7%
The scores are determined as shown below, and the results are shown in Table 2.

[0046]

[Table 2]

All of the plated steel sheets with an electric quantity of 0.5 C / cm ² or less showed a good slidability of "Evaluation 3" or less, whereas the coated samples of more than 0.5 C / cm ² In "5", the slidability is inferior to "Evaluation 5". Especially electricity 0.3C / cm ²
The following plated steel sheets were all "evaluation 1" and showed particularly excellent slidability. From the above results, it is understood that the slidability of the galvannealed steel sheet can be evaluated by the method of the present invention.

[0048]

According to the present invention, even if the alloy phase in the plating layer is very small, the alloy phase can be directly and quantitatively determined by a highly accurate method. Further, according to the present invention, it is possible to quantify the alloy phase for which a quantitative value has not been obtained in the past, and it is expected to have a remarkable effect on the quality improvement and stable production of the product.

Further, according to the present invention, the slidability of the galvannealed steel sheet can be evaluated.

[Brief description of drawings]

FIG. 1 is a graph (calibration curve) showing the relationship between the quantitative value of the alloy phase obtained by the method of the present invention: ζ phase (thickness of ζ phase) and the X-ray diffraction intensity (d = 1.26Å).

FIG. 2 is a graph (calibration curve) showing the relationship between the quantitative value of the alloy phase: Γ phase (thickness of Γ phase) and the X-ray diffraction intensity (d = 2.59Å) obtained by the method of the present invention.

FIG. 3 is a vertical cross-sectional view (a) and a schematic view (b) showing an electrolysis device used in Examples.

FIG. 4 is a graph showing an example of a time-current curve during galvanostatic electrolysis of a galvannealed steel sheet.

[Explanation of symbols]

1 Electrolysis device 2 samples 3 Platinum ring (counter electrode) 4 Saturated calomel electrode 5 platinum wire 6 Electrolyte 7 Reference electrode

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) // G01N 23/20 G01N 27/46 301M (72) Inventor Yoichi Toiyama 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Prefecture Address Kawasaki Iron & Steel Co., Ltd. Technical Research Institute (72) Inventor Kazuno Kyono 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefecture Kawasaki Iron & Steel Co., Ltd. Technical Research Institute F-term (reference) 2G055 AA03 AA07 BA01 BA14 BA20 CA07 CA18 DA08 EA06 EA08 FA01 FA04 FA06 4K027 AA05 AA22 AB05 AB26 AB36 AB37 AE21

Claims (7)

[Claims] 1. A plating layer having a plurality of types of alloy phases in the plating layer as an anode, and the plating layer at each of a plurality of potentials determined based on the immersion potential of the base metal material and the immersion potential of each alloy phase. A method for quantifying alloy phases in a plating layer, which comprises performing constant potential electrolysis of a medium alloy phase and performing phase-specific quantification of each alloy phase in the plating layer based on the amount of electricity flowing at each electrolysis potential. 2. An alloyed hot-dip galvanized steel sheet is used as an anode, and in a zinc sulfate-sodium chloride aqueous solution, potential: -94.
Perform electrolysis within the range of 0 to -920 mV vs SCE potential,
A method for quantifying the ζ phase in a plated layer of a galvannealed steel sheet, which comprises quantifying the ζ phase in the plated layer based on the amount of electricity flowing. 3. An alloyed hot-dip galvanized steel sheet is used as an anode in a zinc sulfate-sodium chloride aqueous solution to have a potential of −94.
Perform electrolysis within the range of 0 to -920 mV vs SCE potential,
The amount of ζ phase in the plating layer is quantified based on the amount of electricity that has flowed, and then the galvannealed steel sheet that is the anode is electrolyzed within the range of potential: -900 to -840 mV to determine the amount of electricity that has flowed. A method for quantifying the ζ phase and the δ ₁ phase in the plating layer of the galvannealed steel sheet, which is characterized by quantifying the δ ₁ phase in the plating layer. 4. An alloyed hot-dip galvanized steel sheet is used as an anode, and in a zinc sulfate-sodium chloride aqueous solution, potential: −94.
Perform electrolysis within the range of 0 to -920 mV vs SCE potential,
The amount of ζ phase in the plating layer is quantified based on the amount of electricity that has flowed, and then the galvannealed steel sheet that is the anode is electrolyzed within the range of potential: -900 to -840 mV to determine the amount of electricity that has flowed. Quantify the δ ₁ phase in the plating layer based on
Subsequently, the alloyed hot-dip galvanized steel sheet as the anode is electrolyzed within a potential range of −830 to −800 mV, and the Γ phase in the plating layer is quantified based on the amount of electricity flowing. Determination method of ζ phase, δ ₁ phase and Γ phase in galvanized galvanized steel sheet. 5. An alloyed hot-dip galvanized steel sheet is used as an anode, and in a zinc sulfate-sodium chloride aqueous solution, potential: -94.
Perform electrolysis within the range of 0 to -920 mV vs SCE potential,
A slidability evaluation method for an alloyed hot-dip galvanized steel sheet, characterized in that an alloyed hot-dip galvanized steel sheet having a good slidability is one in which the amount of electricity flowing is less than a certain amount. 6. The slidability evaluation method according to claim 5, wherein the amount of electricity is 0.5 C / cm ² or less. 7. The sliding of alloyed hot-dip galvanized steel sheet according to claim 5 or 6, wherein the time point when the current density reaches 5 μA / cm ² is the end point of the electrolytic operation. Dynamic evaluation method.